Can You Get Fit in Six Minutes a Week?

Interesting. Talks about intervals. Here is an excerpt:
"...Each of the two groups exercised three times a week. After two weeks, both groups showed almost identical increases in their endurance (as measured in a stationary bicycle time trial), even though the one group had exercised for six to nine minutes per week, and the other about five hours."

If you don't have time for a longer ride then these are a very good replacement. Keep in mind they are extremely taxing to your body and mind so allow for a decent recovery.

I'd say replace an interval session with a micro burst interval session for a month. See how you feel after the month. The only way you are going to be able to determine if a certain training regiment works for you is by trying it.

They're starting from "healthy but not athletes" and I think the biggest gains come when you're just starting out. Theres also no mention of what the "sustainable pace" for the 90 minute rides was, or how long the time trial was that they used for the final test.

The article talks about molecular changes indicating endurance. However, a lot of endurance capability comes from neovascularization, increased mechanical efficiency, increase in blood volume and circulating red blood cells...the list goes on and on. These types of workouts probably won't increase these factors; your body adapts to the stresses you put on it. So, you probably won't get great at an endurance sport by doing only these types of workouts. However, they can be used to supplement other training.